Temporal tissue patterns in bone healing of sheep

Abstract

Secondary fracture healing in long bones leads to the successive formation of intricate patterns of tissues in the newly formed callus. The main aim of this work was to quantitatively describe the topology of these tissue patterns at different stages of the healing process and to generate averaged images of tissue distribution. This averaging procedure was based on stained histological sections (2, 3, 6, and 9 weeks post-operatively) of 64 sheep with a 3 mm tibial mid-shaft osteotomy, stabilized either with a rigid or a semi-rigid external fixator. Before averaging, histological images were sorted for topology according to six identified tissue patterns. The averaged images were obtained for both fixation types and the lateral and medial side separately. For each case, the result of the averaging procedure was a collection of six images characterizing quantitatively the progression of the healing process. In addition, quantified descriptions of the newly formed cartilage and the bone area fractions (BA/TA) of the bony callus are presented. For all cases, a linear increase in the BA/TA of the bony callus was observed. The slope was greatest in the case of the most rigid stabilization and lowest in the case of the least stiff. This topological description of the progression of bone healing will allow quantitative validation (or falsification) of current mechano-biological theories. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J. Orthop. Res. 28: 1440Res. 28: -1447Res. 28: , 2010 Keywords: bone healing; tissue pattern; osteotomy; animal model; averaged image Secondary fracture healing of long bones proceeds via the formation of a callus. 1-3 The task of the callus is to stabilize the fracture fragments resulting in a reduction of the strains in the fracture area, allowing the bone ends to be united. Usually the process of secondary fracture healing is subdivided into three main phases: the inflammatory phase, the reparative phase, and the remodeling phase. 4 These phases, however, are not well separated in time, and significant overlap can occur between them. During the inflammatory phase, vascular damage leads to hematoma formation. The reparative phase includes revascularization and the formation of fibrous tissue and cartilage, and new bone is formed at the periosteal side of the cortex by intramembranous ossification. [4][5][6] Soft callus bridging occurs via cartilage, which is later transformed into bone by endochondral ossification. During the remodeling phase, lamellar bone replaces woven bone, the callus is resorbed, and finally the original shape of the bone is restored. [7][8][9][10] To understand the progression of the healing process, and in particular the influence of the mechanical environment, a number of animal experiments have been performed. In these experiments, either "static" fixators with different degrees of stability [11][12][13][14] or "dynamic" fixators, which induce micro-movement to stimulate callus formation, 15,16 were used. These experiments d...

Follow up of MRI bone marrow edema in the treated diabetic Charcot foot – a review of patient charts

“…Water-like MRI lesions feature both, acute focal inflammation with microvascular hyperpermeability (in bone and in uninjured adjoining soft tissues, due to inflammatory cytokines [30]), and chronic focal hyperemia (from newly grown fibrovascular reparative tissue preceding woven bone callus) [30–32]. Histopathology of active-stage Charcot foot has revealed all of these entities [33,34] as part of the physiologic secondary healing of cortical and cancellous bone fractures [27,30], and of reactive adjoining soft-tissue inflammation like tenosynovitis [35,36].…”

“…Unchanged or stagnant EESC on eleven FUS (in grade 1 cases) was attributed to impaired healing associated with hypertrophic fibrovascular tissue and callus, as indicated by osteosclerosis and joint fusion (ankylosis) seen on plain x-rays obtained simultaneously. Most likely, ineffective immobilization of the bone fragments was the underlying factor, causing hyperplasia of fibrous rather than of mineralized callus [32,40]. …”

Prediction of fracture healing under axial loading, shear loading and bending is possible using distortional and dilatational strains as determining mechanical stimuli

“…Respective tissue compositions show typical patterns of secondary bone healing under axial compressive loading (figure 4) according to Vetter et al [51]. However, in the cases with small IFM (V1, V2, V4), large amounts of intramedullary cartilage are formed, whereas for large IFM (case V3 and V5), this cartilage formation is not visible, according to respective in vivo results [34].…”

“…For both axial load cases, evaluation of the simulated change of tissue distribution over the healing time (figure 3, first two columns) revealed that according to the in vivo results of Vetter et al [51] physiological patterns can be predicted as follows. Initial intramembranous bone formation was predicted periosteally but not in the gap.…”

“…Therefore, we compared our simulated tissue distributions with generally accepted typical patterns for predominant axial loading [51] and predominant shear loading [52] for further corroboration. Vetter et al [51] defined six different healing stages based on histological data after two, three, six and nine weeks. We compared our predictions of the axial load cases A and B to these stages, not regarding stage VI, because remodelling is not covered by our model.…”